Douglas, Schn828, thank you. Yes, Photosynth already ran out of memory at 1,671 photos, and it crashed (Error message) at 1,489 photos, so I had to remove many photos (e.g. the Corner arch, the detailed Sculpture + the pond, etc.) to make room for more interior photos. Synthing 1,395 photos took 4 hours 10 minutes, so I assume this one took at least that long (I started the synth and went to sleep :) In the morning, if it synthed, I got a present. :) If I had infinite computational power and storage, I could easily go over 10,000 photos with this building. :)

About the lack halos, I just looked through the camera position data, and indeed, there seem to be no halos in the entire collection. I'm not sure why this would happen, so we'll need to look closer at the dataset.